On Monday 7/20/15 and Wednesday 7/22/15 I screened out the “160” tanks over 224 micron screens to see if any larvae were ready to settle. This is the same size class used by the hatchery to separate larvae out to put in their setting system. There were less than 5,000, so I figured that by the next Monday there would be enough to set up my setting system. As a reminder, I’m placing 15 4in x 4in white PVC tiles that have been roughed up on one side in a 100 L larvae lank with the hopes that enough larvae set on the tiles. After a few weeks, I will cull larvae to ~20-30 per tile to avoid overcrowding impacting growth. The benefit of using tiles over large shells or cultch (small ground up shell) is that they are easier to standardize for replicates among groups and provide a flat surface for measuring growth rate. Obviously they aren’t a great representation of nature, but will work well to explore the differences in growth rate among the populations.
Larval tank counts
- NF_Tank2_160 (224) -> 30,000 to experiment; 41,175 to NF_Tank2_160
- NF_Tank2_160 (100)
- NF_Tank1_new (100)
- NF_Tank1_new (160) -> NF_Tank2_160
- HC_Tank2_160 (224) -> all 30,000 to experiment
- HC_Tank2_160 (100)
- HC_Tank1_new (100)
- HC_Tank1_new (160) -> HC_Tank2_160
- SS_Tank2_160 (224) -> 30,000 to experiment; 6,000 to SS_Tank2_160
- SS_Tank2_160 (100)
- SS_Tank1_new (100)
- SS_Tank1_new (160) -> SS_Tank2_160
I had at least 30,000 larvae at 224 microns in each group, so I decided to add 30,000 to each of my tile systems. Ryan Crim at the hatchery recommended I add at least four times as many larvae as I want to set. With 15 tiles per tank and at least 200 larvae per tile (to then be culled to 20), this meant I only needed ~12,000 larvae per tank so 30,000 should be plenty.
For the rest of the larvae from NF and SS that weren’t placed in the setting system, I added them back to their respective “160” tanks to deal with later in the week.
There was between 32,000-57,000 larvae from all populations.